Capture Hi-C reveals novel candidate genes and complex long-range interactions with related autoimmune risk loci

Genome-wide association studies have been tremendously successful in identifying genetic variants associated with complex diseases. The majority of association signals are intergenic and evidence is accumulating that a high proportion of signals lie in enhancer regions.We use Capture Hi-C to investigate, for the first time, the interactions between associated variants for four autoimmune diseases and their functional targets in B- and T-cell lines. Here we report numerous looping interactions and provide evidence that only a minority of interactions are common to both B- and T-cell lines, suggesting interactions may be highly cell-type specific; some disease-associated SNPs do not interact with the nearest gene but with more compelling candidate genes (for example, FOXO1, AZI2) often situated several megabases away; and finally, regions associated with different autoimmune diseases interact with each other and the same promoter suggesting common autoimmune gene targets (for example, PTPRC, DEXI and ZFP36L1). Capture Hi-C was carried out to characterise the interactions of confirmed susceptibility loci for four autoimmune diseases: rheumatoid arthritis (RA), type 1 diabetes (T1D), psoriatic arthritis (PsA) and juvenile idiopathic arthritis (JIA) with the aim of linking associated variants with disease-causing genes. We have tested the interactions in two complementary experiments: the first, Region Capture, targets regions associated with disease; the second, Promoter Capture, provides independent validation through capturing all known promoters within 500kb of lead associated disease SNPs. All experiments were performed in human T-cell (Jurkat) and B-cell (GM12878) lines in duplicate.